The present invention relates to adjustable vehicle seats, in particular hydraulically adjustable automotive vehicle seats, and to determining the position of the adjusted vehicle seat.
In order to comfortably accommodate various sizes and shapes of occupants vehicle seats are generally provided with various adjustment mechanisms to adjust the position of the seat within the vehicle and/or move various movable portions of the seat. Typically for example vehicle seats are provided with multiple adjustments including fore and aft adjustment, and seat back pivotal adjustment to adjust the angle of the seat back to the bottom cushion of the seat can be adjusted. Other adjustments may also be provided to, for example, adjust the height of the vehicle seat, angle and tilt of the seat bottom cushion, position of the headrest, and/or the lumber support etc. More and more seat adjustment is now increasingly being demanded.
The seat adjustment, or at least the main seat adjustments are increasingly power operated. Power operated arrangements conventionally utilise multiple individual electric motors to drive each adjustment. It has also been proposed to utilise hydraulic adjustment arrangements comprising hydraulic actuators operatively connected between the movable portions of the seat with suitable control valves to prevent fluid flow and lock the seat position. An example of a powered hydraulic adjustment system is described, for example, in U.S. Pat. No. 5,435,625.
Hydraulic powered arrangements offer the prospect of extremely quiet, near silent, smooth and almost infinitely variable adjustment operation without noisy mechanical gearing. In spite of this hydraulic adjustment arrangements have not been widely adopted principally due to perceived complexity and high cost. Improvements to conventional hydraulic adjustment systems, in particular addressed to reducing the costs and complexity would therefore be generally desirable in order to allow such systems, with their advantages, to be practically implemented.
In relation to hydraulic systems a distinction must be drawn between hydraulic or fluid powered adjustment systems, and the more basic and simple hydraulic locking systems and/or damper arrangements.
Many powered adjustment systems (including both electric or hydraulic) also include seat position measurement arrangements to determine the adjusted position of at least some of the seat adjustment in order to monitor and/or control the seat adjustment. Such arrangements in particular also allow a specific seat position for a particular occupant to be stored in a memory and the seat then automatically adjusted to this preset seat position. Measurement of the seat position may also be used to alter the settings of various occupant protection systems, for example the vehicle airbags, in order to optimise the protection when the seat is in a particular position.
Conventional seat position measurement arrangements comprise individual sensor arrangements which are provided in association with each seat adjustment. For example individual shaft encoders may be used with the various seat adjustment electric drive motors to monitor their operation and rotation and number of revolutions, from an initial position and determine the adjusted position. Other seat position measurement arrangements may also be used to more directly measure and monitor the adjusted position of various different seat adjustments.
Whilst such seat position measurement arrangements function adequately, as the number of seat adjustments provided and to be monitored increases the number of individual seat position sensors that are required in such conventional seat adjustment systems increases. This undesirably adds to the complexity of the seat and seat control system with the additional sensor arrangements and additional wiring increasing costs, making assembly more difficult and costly, and possibly also increasing reliability problems with their being further scope for failure of the multiple individual sensor arrangements.
Furthermore with hydraulic powered systems direct seat position measurement arrangements are typically required to for example measure the extension of the respective hydraulic cylinder actuators, or seat adjustment itself, which can be relatively complex, costly, and are susceptible to damage.
It is therefore desirable to provide an improved system and method for vehicle seat adjustment which addresses the above mentioned problems and/or which offers improvements or an alternative to conventional arrangements. In particular it is desirable to provide a vehicle seat adjustment position measurement system and method for a hydraulic vehicle seat adjustment system which is simpler, cheaper, and more reliable.